1. Field of the Invention
This invention relates to automatic fluid pressure monitoring systems, and in particular such systems wherein the air brake pressure of a train-line system is monitored to provide signal outputs indicative of the air pressure conditions therein on a continuous basis.
2. Prior Art
Continuous air brake monitoring systems are well known to the art. For example, U.S. Pat. No. 3,944,287 provides continuous monitoring of both a dynamic brake pressure and pneumatic brake pressure for a railroad vehicle and also provides an indication of the accumulative braking pressure of the dynamic brake and the pneumatic brake. Pressure monitoring of multi-line brake systems has been accomplished by utilizing a pressure sensitive switch in each of the brake lines and which is actuatable when the pressure in that line reaches a predetermined threshold value. Such a system is exemplified by the disclosures of U.S. Pat. Nos. 3,593,265 and 4,025,781.
Additionally, complex systems have also been utilized involving an analysis of an electrical waveform for determining an abnormal hydraulic pressure in a brake circuit such as is exemplified by the disclosure of U.S. Pat. No. 3,652,985. Other systems are known which, in addition to responding to an absolute pressure level, also respond to rate and duration of pressure drop, as represented by the disclosure of U.S. Pat. No. 4,051,467. Fluid pressure monitoring systems may also rely upon detection of a drop in fluid pressure when such drop occurs for a given or predetermined period of time such as presented by the disclosure of U.S. Pat. No. 3,748,656.